Abstract: An external basic input/output system (BIOS) device for a computer is disclosed. The device includes an external memory module and a motherboard pin interface. The backup BIOS is stored in the external memory module. When the main BIOS is damaged, the external backup BIOS can replace the main BIOS to execute power-on procedures of the computer. The backup BIOS can also recover the correct data to the damaged main BIOS. The external backup device needs to be installed only when a severe error occurs in the main BIOS. Therefore, the present invention reduces the cost of motherboards and at the same time offers the advantages of a conventional dual BIOS system.